1. Field of the Invention
The invention relates to the field of electronic reproduction technology and relates to a method and an apparatus for determining the dimensions of engraved sample cells in an electric engraving machine for engraving printing cylinders for gravure printing, and also such an engraving machine.
In an electronic engraving machine, an engraving element with an engraving gouge as a cutting tool moves in an axial direction along a rotating printing cylinder. The engraving gouge, controlled by an engraving control signal, cuts a sequence of cells disposed in an engraving pattern into an outer surface of the printing cylinder. An engraving control signal is formed by superimposing image signal values, that represent engraved tonal values between xe2x80x9clightxe2x80x9d and xe2x80x9cdepthxe2x80x9d, with a periodic scanning signal. While the scanning signal has the effect of a vibrating reciprocating movement of the engraving gouge in order to produce the engraved pattern, the image signal values determine the geometric dimensions of the cells engraved into the outer surface of the printing cylinder.
Before the actual engraving, during a so-called sample or test engraving, sample cells for predefined tonal values are engraved on the printing cylinder. After the sample cut, the actual geometric dimensions of the engraved sample cells are measured by a cell measuring apparatus and are compared with predefined desired geometric dimensions of the cells. From the value comparison, setting values are obtained with which the engraving control signal is then calibrated in such a way that the cells actually produced during the subsequent engraving correspond to the cells required for correct tonal value reproduction.
U.S. Pat. No. 5,293,426 discloses a method and an apparatus in the form of a measuring microscope for determining the dimensions of engraved sample cells in an electric engraving machine for engraving printing cylinders, and also such an engraving machine.
U.S. Pat. No. 3,931,570 describes a portable measuring apparatus for measuring the volume of engraved cells.
The cell measuring apparatus often used is a video camera. In this case, the actual geometric dimensions of the engraved sample cells are measured electronically in the video image recorded by the video camera.
In order to engrave printing cylinders for magazine printing, in practice a plurality of engraving machines are used, on which sample engravings have to be carried out. It then proves to be expedient, in order to measure the sample cells engraved with the individual engraving machines, to use only a single cell measuring apparatus, in order not to have to take account of tolerances which inevitably occur when a plurality of cell measuring apparatuses are used.
It is accordingly an object of the invention to provide a method of measuring cells and a device for measuring the cells that overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which simple and accurate measurement of the engraved sample cells is made possible, in particular when a large number of engraving machines are used.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for determining dimensions of an engraved cell formed by an electronic engraving machine for engraving printing cylinders for gravure printing. During a test engraving period, test cells are engraved with desired dimensions defining predefined desired tonal values. An engraving element controlled by an engraving control signal is used for engraving a sequence of cells into a rotating printing cylinder resulting in engraved cells. Actual dimensions of the engraved cells represent actual tonal values. A measuring apparatus constructed as a mobile cell measuring instrument is provided and is placed on the printing cylinder to be measured. The actual dimensions of the engraved cells are measured using the mobile cell measuring instrument and the actual dimensions are compared with the desired dimensions determining the predefined desired tonal values, to obtain setting values for calibrating the engraving control signal such that the actual tonal values correspond to the desired tonal values. The actual dimensions of the engraved cells determined with the mobile cell measuring instrument are transmitted wirelessly to a measured value receiver for further processing.
In accordance with an added mode of the invention, there is the step of placing the measured value receiver in a fixed location.
In accordance with an additional mode of the invention, there is the step of carrying out a transmission of the actual dimensions only during a calibration period of the engraving control signal.
In accordance with another mode of the invention, there is the step of controlling functions of the mobile cell measuring instrument using a manually operated, mobile operating instrument.
In accordance with a further mode of the invention, there are the steps of generating control commands in the mobile operating instrument; and transmitting the control commands for controlling the functions of the mobile cell measuring instrument wirelessly from the mobile operating instrument to the mobile cell measuring instrument.
In accordance with another added mode of the invention, there is the step using the mobile operating instrument for controlling a positioning of the mobile cell measuring instrument with respect to the printing cylinder.
In accordance with another additional mode of the invention, there is the step of using the mobile operating instrument for controlling a focusing of the mobile cell measuring instrument onto the printing cylinder.
In accordance with a further added mode of the invention, there is the step of using the mobile operating instrument for controlling an illumination of the engraved cells.
In accordance with a concomitant mode of the invention, there is the step of operating the mobile cell measuring instrument and/or the mobile operating instrument with a rechargeable operating voltage source.
With the foregoing and other objects in view there is further provided, in accordance with the invention, an apparatus for determining dimensions of engraved cells formed by an engraving machine for engraving printing cylinders for gravure printing. The apparatus contains a measured value receiver, and a mobile cell measuring instrument to be placed on a printing cylinder to be measured to determine the dimensions of the engraved cells. The mobile cell measuring instrument has an integrated measured value transmitter for transmitting the dimensions of the engraved cells wirelessly to the measured value receiver for further processing.
In accordance with an added mode of the invention, the mobile cell measuring instrument includes a video camera to record a video image of the engraved cells; an illumination source for illuminating the engraved cells; and an image evaluation stage connected to the video camera for determining the dimensions of the engraved cells by electronic evaluation of the video image provided by the video camera. The image evaluation stage is also connected to the measured value transmitter for the wireless transmission of the dimensions of the engraved cells. In addition, the measured valued receiver is a fixed-location measured value receiver.
In accordance with an additional feature of the invention, the mobile cell measuring instrument has a rechargeable operating voltage source.
In accordance with another feature of the invention, the illumination source can be controlled in order to correct an illumination of the engraved cells.
In accordance with a further feature of the invention, the mobile cell measuring instrument has a controllable positioning device that is operatively connected to the video camera for positioning and/or focusing the video camera.
In accordance with another further feature of the invention, the mobile cell measuring instrument has a control stage connected between the positioning device and the illumination source to control the positioning device and/or the illumination source as a function of control commands received.
In accordance with another added feature of the invention, the mobile cell measuring instrument has a control command receiver connected to the control stage and receives the control commands wirelessly.
In accordance with another additional feature of the invention, the mobile cell measuring instrument has a control monitor for monitoring a measuring operation and is connected to the video camera.
In accordance with yet another feature of the invention, a manually operated, mobile operating instrument for generating the control commands is provided. The mobile operating instrument has a control command transmitter for transmitting wirelessly the control commands to the mobile cell measuring instrument.
In accordance with a further feature of the invention, the mobile operating instrument has a manually operated keyboard connected to the control command transmitter and a manually operated positioning device connected to the control command transmitter. The control commands are generated in the mobile operating instrument by use of the manually operated keyboard and by the manually operated positioning device.
In accordance with an added feature of the invention, the mobile operating instrument has a rechargeable operating voltage source.
In accordance with an additional feature of the invention, the mobile operating instrument is activated by an enable command received from the engraving machine.
With the foregoing and other objects in view there is additionally provided, in accordance with the invention, an engraving machine for engraving printing cylinders for gravure printing. The engraving machine contains a first drive for driving and mounting a printing cylinder so as to be capable of rotating the printing cylinder; an engraving element, acted on by an engraving control signal, for engraving cells into the printing cylinder; a second drive coupled to the engraving element for moving the engraving element along the printing cylinder; a signal conditioning stage for generating the engraving control signal and connected to the engraving element; and a sample engraving computer connected to the signal conditioning stage. The sample engraving computer formulates engraving control signal values for engraving the cells. A measuring apparatus is provided for measuring actual dimensions of the cells representing actual tonal values to be compared with desired dimensions representing predefined desired tonal values in order to obtain setting values for calibrating the engraving control signal. The measuring apparatus is a mobile cell measuring instrument disposed on the printing cylinder to be measured and has an integrated measured value transmitter. A fixed-location measured value receiver is connected to the sample engraving computer. The actual dimensions of the cells engraved determined by the mobile cell measuring instrument are transmitted wirelessly by the integrated measured value transmitter to the fixed-location measured value receiver for further processing.
In accordance with another feature of the invention, the mobile cell measuring instrument includes: a video camera to record a video image of the cells; a positioning device operatively connected to the video camera and receiving control commands for at least one of positioning and focusing the video camera; an illumination source, receiving and controlled by the control commands, for illuminating the cells; an image evaluation stage connected to the video camera for determining the actual dimensions of the cells by an electronic evaluation of the video image provided by the video camera; a rechargeable operating voltage source; and a measured value transmitter connected to the image evaluation stage. The measured value transmitter provides a wireless transmission of the actual dimensions of the cells to the fixed-location measured value receiver.
In accordance with a concomitant feature of the invention, a manually operated, mobile operating instrument for generating the control commands is provided. The mobile operating instrument has a control command transmitter for transmitting wirelessly the control commands from the mobile operating instrument to the mobile cell measuring instrument.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of measuring cells and a device for measuring the cells, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.